The collaborative program between the Stanford Department of Physics and the Division of Cardiology has, over the past four years, resulted in an operational facility to measure and study the magnetic fields produced by the human heart. Electrophysiological considerations in the heart and examination of current flow through the body strongly suggest that the vector magnetocardiogram (VMCG) may be more sensitive or more specific to certain cardiac abnormalities than the ECG. Preliminary measurements on human subjects over the past two years have been very encouraging. The purpose of the proposed research is simply to verify whether the VMCG is a valuable tool in the diagnosis of diseases resulting in S-T segment changes. We have chosen this class of diseases because: 1. There is a clear need for a new, noninvasive technique to improve reliability of diagnosis of these diseases; and, 2. Theoretical considerations suggest that the VMCG may be highly sensitive to these abnormalities. Two recent developments make us optimistic that magnetocardiography can become a useful clinical tool. The recent presentation of our data from experiments in dogs has confirmed that our measurement techniques, the unipositional lead system, accurately measures the magnetic heart vector (MHV). Conversely, it was also shown that the practice of mapping the normal component of magnetic field over the entire chest does not lead to a good determination of the cardiac currents. Second, with the acquisition of a new state-of-the-art magnetometer, we can now make measurements outside of our magnetic shield. The accuracy and simplicity of the unipositional lead system, and the fact that measurements must no longer be made in a magnetically-shielded room make us confident that magnetocardiography can become a widely used clinical tool.